This invention relates generally to the field of high speed data networks and, in particular, to a smearing distributor for a high speed data network that enables the network to provide paths of adaptive capacity from an external information source to an external information sink.
The explosive growth of the Internet and a corresponding increase in the computing capacity of computers for accessing the Internet have created a strong impetus for designing networks that can provide the capacity required to support new service opportunities. The current structure of the Internet is a complicated interconnection of intricate nodes that require complex protocols for data transfer. The configuration, installation and maintenance of the equipment and the operation of the Internet requires a large work force having knowledge and extensive experience.
There is a growing acceptance of the proposition that in order to realize its potential, at least the backbone of the Internet must be simplified to enable scalability and improve throughput to provide bandwidth to support innovative application development at the network edges.
Applicant has long realized and advocated the advantages of simplifying network structures and network protocols to enable a high capacity network capable of serving as a backbone for the next generation Internet. Steps toward providing a simplified network structure and protocol include inventions described in the following United States Patent Applications to the Applicant:
U.S. patent application Ser. No. 09/132,465 which was filed on Aug. 11, 1988 and entitled UNIVERSAL TRANSFER METHOD AND NETWORK WITH DISTRIBUTED SWITCH, the specification of which is incorporated herein by reference;
U.S. patent application Ser. No. 09/244,824 which was filed on Feb. 4, 1999 and entitled RATE CONTROLLED MULTI-CLASS HIGH-CAPACITY PACKET SWITCH, the specification of which is also incorporated herein by reference; and
U.S. patent application Ser. No. 09/286,431 which was filed on Apr. 6, 1999 and entitled SELF-CONFIGURING DISTRIBUTED SWITCH, the specification of which is likewise incorporated herein by reference.
It is well understood in the art that decisions respecting the architecture of data networks have a lasting impact on network economics, operations and performance. Wavelength-division multiplex (WDM) optical links have become a popular medium for data transfer. In a WDM optical link, light of two or more wavelengths is used for the simultaneous transfer of binary data streams. WDM optical links are typically used as a collection of individual data channels, each wavelength representing a single data channel. This affects both traffic efficiency and network scalability. The combined data traffic capacity of the channels of a W-channel WDM link is less than that of a W-channel shared link. The scalability of WDM networks depends largely on the network architecture and mode of operation. If channel-switching is used in the core of switches in the network, the data traffic capacity of the network is limited by the speed at which the channels can be switched and the rate at which network switches can be reconfigured. If packet switching is used in the core of switches in the network, the network capacity is determined by the rate at which packets can be switched in the core. There is a disadvantage of using WDM optical links as a collection of individual data channels, because that limits the maximum bandwidth that can be assigned to a connection to the bandwidth capacity of a single data channel. Consequently, there exists a need for a network architecture that enables more flexible connection granularity.
It is well known that routing protocols used in the Internet are complex. A problem that arises due to the complexity of Internet routing protocols is the knowledge required to operate the network. A very large work force is employed to set up and maintain links to the Internet because of the complexity and limitations of the protocols used to transfer data. Significant efficiencies could be realized if the backbone of the Internet were substantially passive in such a way that it were substantially xe2x80x9cinvisiblexe2x80x9d to users. An xe2x80x9cinvisiblexe2x80x9d network is a network that accepts connections from a plurality of edge protocols without requiring complex interfaces to perform protocol conversions, and delivers data to a data sink in a format in which the data was received from a data source.
There therefore exists a need for a network which provides compliant, invisible paths for a number of different data transfer protocols.
It is therefore an object of the invention to provide a WDM data network that includes smearing distributors to enable higher connection bandwidth.
It is a further object of the invention to provide a WDM data network that includes smearing distributors to enable compliant, invisible paths for a wide range of data transfer protocols.
The invention therefore provides a smearing distributor for a wavelength-division multiplexed (WDM) data network. The smearing distributor includes a demultiplexer for demultiplexing the channels of an incoming WDM communications link having W channels, W smearing units, and a passive Wxc3x97W rotator having a plurality of input ports and a plurality of output ports. Each input port of the passive rotator is adapted to connect to a smearing unit which is connected to a channel of the communications link, and each output port of the passive rotator is adapted to connect to a respective input port of a plane of a parallel-plane switch.
Each smearing unit sorts the data segments it receives into N queues, N being the number of outgoing WDM links connected to the parallel-plane switch, and transfers each data segment to an output port so that data segments from any one of the N queues are transferred to the output ports in a substantially even distribution.
There is a smearing distributor associated with each communications link in the WDM network. The number of input ports on the smearing distributor equals the number of channels in a WDM communications link.
Each smearing unit tracks the plane of the parallel-plane core module to which a last data segment was transferred. This is done to ensure that data segments to be routed to an outgoing WDM link are transferred to sequential planes of the parallel-plane core module. Consequently, the data segments routed to a given outgoing WDM link are transferred in an order in which a data segment is only transferred to a plane adjacent the plane to which a last data segment routed to the same outgoing WDM link was transferred.
The invention further provides a wavelength-division multiplexed data network comprising a plurality of rate-regulated ingress edge modules, each of the edge modules having a plurality of ingress ports and a plurality of output ports. The ingress ports are connected by communications links to data packet sources. A plurality of smearing distributors having a plurality of input ports and a plurality of output ports are located between the edge modules and core modules. Each of the smearing distributors is respectively connected by a communications link to a respective one of the edge modules. Each communications link consists of a plurality of communications channels respectively providing a connection between an output port of the edge module and an input port of the smearing distributor. The core modules comprise parallel-plane switches, each plane of the parallel-plane switches having a plurality of input ports and a plurality of output ports, each input port being connected to a corresponding output port of one of the smearing distributors. The smearing distributors are adapted to ensure that consecutive data packets destined for the same output link are distributed substantially equally among the planes of the parallel-plane switch.
Preferably, the communications links used to interconnect the edge modules and the core modules are wavelength-division multiplexed (WDM) optical links that support a plurality of channels. The smearing distributor has one input port and one output port for each of the channels in the communications links. The number of planes in the single-stage space switch preferably equals the number of ports of each smearing distributor.
In one embodiment, each output port of each plane of the parallel-plane switch is connected directly to an input port of an egress edge module by a connumications channel, the egress edge module having a plurality of egress ports connected to data packet sinks.
As an alternative, in a second embodiment, the core modules may also be interconnected to permit more flexible routing and increase scalability. If the core modules are interconnected, a smearing distributor is located on each link between an output side of the first core module and an input side of the second core module. Carefully constructed routing plans minimize the number of hops required to establish a connection. Thus, the network may include a second core stage including a second plurality of smearing distributors connected by a plurality of communications links to the output ports of the planes of a parallel-plane switch, and a second parallel-plane switch, each plane of the parallel-plane switch being connected by a communications channel to a corresponding output port of one of the second plurality of smearing distributors. In this configuration, an output port of each plane of the second parallel-plane switch is connected by a communications link to an input port of an egress edge module.
Successive pluralities of smearing distributors followed by parallel-plane switches can be configured. However, a large number of stages is neither necessary nor desirable.
The high-speed WDM data network in accordance with the invention provides a number of advantages. For example, the capacity is scalable from a few Terabits per second (Tb/s) to several Exabits per second (Eb/s), while the per-connection bandwidth allocation can range from a few Kb/s to about one Tb/s. The scalability of the WDM network permits the number of edge modules to be scaled to several millions. The number of data flows from (to) an edge module can also be varied from a few, to millions of simultaneous connections.
The efficient use of each WDM link as a single medium, while still providing connectivity with fine granularity and virtually eliminating data blocking in a potentially large modular core enables the WDM network in accordance with the invention to be scaled to meet the foreseeable requirements of the next generation Internet.